A. Field of the Invention
The present invention relates to apparatus for use in the drilling and operation of wells, particularly oil wells and geothermal wells. More particularly, the invention relates to novel modular actuator and hydraulic assemblies and a novel control apparatus for use with existing oil well blow-out preventers of the type used to prevent pressurized subterranean liquids or gases from blowing out and upwards through a well hole.
B. Description of Background Art
In drilling for natural gas or liquid petroleum, a drill string consisting of many lengths of threaded pipes screwed together and tipped with a drill bit head is used to bore through rock and soil. The drill bit head has a larger diameter than the pipes forming the drill string above it. A rotary engine coupled to the upper end of the drill string transmits a rotary boring action to the drill bit head.
During the drilling operation, a specially formulated mud is introduced into an opening in an upper drill pipe. This mud, which typically is selected to have a high specific gravity, flows downwards through the hollow interior of the pipes in the drill string and out through small holes or jets in the drill bit head. Since the drill bit head has a larger diameter than the drill string above it, an elongated annular space is created between the drill string pipes and the bore hole wall during the drilling process. The annular space permits the mud to flow upwards to the surface. Mud flowing upwards carries drill cuttings, primarily rock chips, to the surface. The mud also lubricates the rotating drill string, and provides a downward hydrostatic pressure which counteracts pressure which might be encountered in subsurface gas pockets. A steel tubular well casing is inserted into the bore hole when the drilling operation has been completed.
In normal oil well drilling operations, it is not uncommon to encounter subsurface gas pockets whose pressure is much greater than could be resisted by the hydrostatic pressure of the elongated annular column of drilling mud. To prevent the explosive and potentially dangerous and expensive release of gas and/or liquid under pressure upwards out through the drilling hole, Blow-Out Preventers (BOP's) are used. Blow-out preventers are usually mounted to a drill pipe or well casing near the upper end of the bore hole. The blow-out preventers are mounted to drill string components such as a drill pipe or well casing tubes, and function by shutting off upward movement of a gas, liquid or drill string components which could be forced upwardly in response to pressure encountered in an oil or gas reservoir.
Typical oil or gas well drilling or production operations utilize a vertical stack of blow-out preventers of various types. The stack usually includes an annular type of blow-out preventer which is located at the upper end of a stack, located near a well-head.
Annular blow-out preventers have a resilient sealing means which can be forced by hydraulic cylinders into compressive sealing contact with the outer circumferential surface of various diameter drill string components or well casings, preventing pressure from subterranean gas pockets from blowing out material along the drill string and up the bore hole. Usually, the resilient sealing means of a blow-out preventer is so designed as to permit abutting contact of a plurality of sealing elements, when all elements of a drill string are removed from the casing. This permits complete shutoff of the well, even with all drill string elements removed. Most oil well blow-out preventers are remotely operable, as, for example, by a hydraulic pressure source near the drill hole opening having pressure lines running down to hydraulic actuator cylinders of the blow-out preventer.
Most blow-out preventer stacks also include a series of longitudinally spaced apart blow-out preventers of various types, located below an upper annular blow-out preventer. Other types of blow-out preventers include pipe ram, blind ram and shear ram. Construction and operation of blow-out preventers of the types identified above are described at http://en.wickipedia.org/wiki/blowout-preventer.
The present invention was conceived of in part to provide a modular control apparatus for oil well blow-out preventers, the apparatus including novel air actuator/hydraulic valve assemblies which are mounted to a compact hydraulic manifold, and including a novel actuator air control panel for remotely energizing pneumatic air cylinder-actuators which operate an integral hydraulic valve of each actuator/valve assembly.